Charles R. Krause, Richard C. Derksen, LeonaE. Horst, Ross D. Brazee, Michael G. Klein, and MichaelE. Reding, U.S. Department of Agriculture, Agricultural Research Service, Application Technology Research Unit, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, Ohio; Randall Zondag, Ohio State University Extension, Lake County.
Bioassay and Leaf Analysis
Sample holders used for mounting samples for scanning electron microscopy (SEM) called stubs, each with conductive, adhesive specimen mounts (Ted Pella, Tustin, Calif.), were mounted in trees before each treatment. Leaves and stubs were collected from each treatment after each spray for bioassay and electron beam analysis (EBA), a combination of SEM and energy dispersive X-ray analysis (EDXA). Leaves from each treatment were collected after each spray and freshly mounted on stubs using adhesive specimen mounts.
A cold field emission scanning electron microscope (CFESEM) and a variable pressure scanning electron microscope (VPSEM), both equipped with EDXA, located at the Molecular and Cellular Imaging Center at The Ohio State University's Ohio Agricultural Research and Development Center's (OSU/OARDC), Wooster campus, were used for EBA. Electron beam analysis permitted direct visualization and identification of the pathogens, morphologically, and chemical characterization of any fungicide present.
The fungicide used in this study was Mankocide, a combination of Cu(OH)2 and mancozeb that permitted EBA identification based on the presence of Cu, MN, and Zn in the molecule.